Words by Ms Anne Sebba, author of That Woman:
The Life of Wallis Simpson, Duchess of Windsor

When Edward VIII was still Prince of Wales some of the worst arguments he had with his father George V were over jazz, cocktails, painted fingernails, use of the telephone and - trouser turn-ups. Extraordinary as it may seem, when other countries were involved in existential struggles or assassinating their leaders, nothing inflamed the King of England more - where his son was concerned - than his determination to be modern and his love of all things American.

Ms Wallis Simpson, the American woman he loved so obsessively that he gave up his throne to be with her, was also well known for her style. Even when she was an impoverished Baltimore debutante she wanted the latest fashions but with a twist, something that would mark her out from the crowd, so she and her mother used a dressmaker to copy celebrity gowns she had seen in magazines. And once Ms Simpson came to Europe with her second husband, Mr Ernest Simpson, she took to visiting Paris couture houses that she could ill afford. It was no coincidence that when she met the Duke for the first time she happened to have one or two new Parisian outfits ready in her wardrobe. But he, in spite of his pursuit of whatever was modern and American, also loved the tweed and tartan of his native land, often mixing them in wildly flamboyant combinations and kept serried rows of kilts in a wide variety of cloth in his wardrobe. According to that arbiter of taste, Ms Diana Vreeland, the Duke "had style in every buckle on his kilt, every check of his country suits". Ms Simpson did not much like the country look and commented in her memoirs on the Duke's "very loud checked tweeds" when they first met. But he never stopped wearing them. When photographer Lord Lichfield, the Queen's cousin, photographed him in the 1960s wearing a checked overshirt and tartan trousers with paisley cravat and argyle socks, one fashion writer called this "an audacious mix"; eccentric might be more accurate. His ties, however, were fairly plain but it was for these that he is famous. The Duke had them made with extra-thick inner linings in order to achieve a fatter knot, thus giving rise to the sartorial invention with which he is still today associated - the Windsor knot, although this may in fact have been named not after him, but after his grandfather Edward VII. One of his less noisy fashion choices was an ink blue, double-breasted dinner jacket with black satin lapels for formal eveningwear instead of the stiff shirts and tail coats of an earlier era.

After the abdication in 1936 and subsequent marriage, looking glamorous and expensively dressed became something of a mantra for the Duke and Duchess. It was their armour

But after the abdication in 1936 and subsequent marriage, when the couple were granted the title of Duke and Duchess of Windsor and lived abroad, looking glamorous and expensively dressed became something of a mantra for them both. It was their armour. From 1937 onwards Ms Simpson regularly appeared on lists of the world's best-dressed women. It was her way of showing up her sister-in-law, Elizabeth, the new queen - who she blamed for causing so much ill feeling towards the Duke - as a dowdy, frumpy dresser and saying to the rest of the world "look what you missed". This was especially important at a time when the royals did not give interviews, so clothes had to do the talking for them.

The Duke, equally furious with his family for refusing to allow Ms Simpson to style herself HRH, determined to do whatever he could to make up to her what he believed she had been forced to give up. So they became important collectors and connoisseurs of modern jewellery and the clothes were usually simple and elegant in order to show off the magnificent jewellery.

The gifts had begun in 1935: "not many pieces but awfully nice stones", Ms Simpson had explained to her aunt. Once they were married the gifts intensified. The Duke even visited Cartier in Paris just before the fall of France with all the terror, privation and dislocation that was surrounding him, bearing pockets full of stones and instructions to make up a very special piece, apparently oblivious that his requirements for the production of such a jewel in wartime might strike some as insensitive. The bold diamond flamingo clip, with startling tail feathers of rubies, sapphires and emeralds, was made in Paris in 1940 according to his specific instructions for the brooch to have retractable legs so that Ms Simpson could wear it centrally without a leg digging into her ribs if she bent down. Wearing this magnificent three-dimensional flamingo with its brilliant plumage would have been audacious at any time. Ms Simpson, who used jewellery not simply as a display of wealth but to express her bold style and above all her personality, wore it as she set off on her controversial 1941 visit to the United States with the Duke. She also had some magnificent jewelled powder compacts "and was always making up at table, which of course is very sexy," commented decorator Mr Nicholas Haslam. It was certainly modern in a brash kind of way.

The most lasting modern contribution Edward VIII made during his brief reign as king was to make acceptable the search for individual or personal happiness

Ms Simpson's desire to be modern occasionally led to some ghastly faux pas. Although both of them dieted ferociously, her broad shoulders did not suit the so called "new look" of Dior in 1947 with big skirts and strapless bodices. Nor did a later experiment with hot pants. But she did make acceptable the short cocktail dress that showed off her slim legs to good advantage.

Ultimately the most lasting "modern" contribution Edward VII made during his brief reign as king was nothing to do with clothes but was to make acceptable the search for individual or personal happiness, something for which his mother, Queen Mary, never forgave her daughter-in-law. Nor did she ever learn to use the telephone.

That Woman: The Life of Wallis Simpson, Duchess of Windsor by Ms Anne Sebba (Weidenfeld and Nicolson, £20) is out now. W.E., the biopic about the couple directed by Madonna, has just previewed in Venice